Commercial roofing in Yakima and Naches: TPO, PVC and built-up

Local code allows two roof layers, but the default here is to take everything off so the substrate can be inspected and repaired. The exception is a built-up roof whose base layer is adhered to the deck and near impossible to remove. In that case the crew removes every layer above it and roofs over the first one. On the Naches Fruit Stand it was a worn-out four-layer roof, stripped down, resheeted in 7/16 OSB, then covered with 60 mil TPO welded in place.

The same sequence ran at Decco USA, where a metal roof came off, 7/16 OSB went down over the metal substrate, and TPO rolls up to 100 feet long were laid and secured with plates. A telehandler fed materials to the roof, the seams were probed for a watertight finish, and every vent and penetration got its own flashing detail. At LabCorp in winter 2022 and Syntec US in March 2024 the starting point was a built-up roof torn off to the deck. Syntec also got a new roof drain.

Which membrane? TPO is the less expensive one, it is white and reflective for Yakima's hot summers, and it is recyclable. PVC costs more and is more rigid to detail, but it holds up better to chemicals, heavy foot traffic and heat. They also ran their own fire test on both. TPO kept burning once it was lit. PVC stopped burning as soon as the flame was removed. If the building has high traffic, chemical exposure or a fire-safety concern, that result matters. Roofs below a 3:12 pitch can also take standing seam metal with a manufactured seal on the panel that creates a watertight seam when crimped.